The present invention relates to a method and a device for detecting cornering of a vehicle. Such a method, i.e. such a device detects a signal that indicates cornering. Such a signal that indicates cornering can be the curve radius, the transverse acceleration, or a signal containing comparable information. Methods for detecting cornering are described, for example, in EP 0 377 645 B1 and EP 0 376 984 B1. Under certain conditions, it has been shown that these methods do not indicate cornering with enough precision. This is especially true in vehicles equipped with an anti-lock braking system (ABS), a traction control system (TCS), or an electronic stability program (ESP). Further details regarding ABS, TCS, and ESP can be taken, e.g. from the article xe2x80x9cFDRxe2x80x94die Fahrdynamikregelung von Boschxe2x80x9d (ESPxe2x80x94the Electronic Stability Program of Bosch), by A. van Zanten, R. Erhardt, and G. Pfaff, ATZ Automobiltechnische Zeitschrift (Automobile Technology Magazine), 96 (1994) 11, pages 674 to 689.
For example, the known methods for detecting cornering can often not determine cornering precisely enough at wheels or axles, at which measures influencing operating dynamics are implemented, such as braking actions, ABS control actions, TCS control actions, or control actions from an electronic stability program. This is also apparent in the case of braking on a so-called split-friction road surface, i.e. roadways having a different coefficient of friction on the left and right sides of the vehicle. The known method cannot reliably differentiate such braking from braking while cornering.
Correspondingly, the object of the present invention is to provide an improved method and device for detecting cornering of a vehicle.
The object of the present invention is achieved by a method according to claim 1, and by a device according to claim 11. To detect cornering of a vehicle or to ascertain the transverse acceleration of a vehicle, a signal indicating vehicle cornering, a measure of the curve radius, or the transverse acceleration of the vehicle is determined in this case, using a reference speed for at least one side of the vehicle; a reference speed of a side of the vehicle being determined as a function of the deceleration of at least one wheel on this side of the vehicle. In this context, an example of a signal indicating cornering of the vehicle can be the curve radius, the transverse acceleration of the vehicle, or the difference of the reference speeds of the two sides of the vehicle. In this manner, cornering is clearly detected more precisely, and in particular, more reliably.
In an advantageous refinement of the present invention, the speed of the wheel is ascertained, e.g. measured, and the deceleration of the wheel is determined by differentiating the wheel speed with respect to time.
In an advantageous further refinement of the present invention, the reference speed of the wheel is set equal to the speed of the wheel, when the deceleration of the wheel is less than or (essentially) equal to the deceleration of the vehicle, after the vehicle deceleration is increased by means of a weighting value.
In another advantageous refinement of the present invention, the reference speed of the wheel is interpolated, when the deceleration of the wheel is greater than the deceleration of the vehicle, after the vehicle deceleration is increased by means of a weighting value.
In an additional advantageous refinement of the present invention, the reference speed is interpolated according to the equation
vs,neu=vs,altxe2x88x92xcex1afzxcex94t
where
vs,neu is the interpolated value of the reference speed,
vs,alt is the previous value of the reference speed,
xcex1 is a constant, which is advantageously the weighting value,
afz is the deceleration of the vehicle, and
xcex94t is the cycle time for the interpolation.
In a further advantageous refinement of the present invention, the deceleration of the vehicle is multiplied by the weighting value.
In another advantageous refinement of the present invention, the weighting value is formed as a function of the driving situation.
In another advantageous refinement of the present invention, the weighting value assumes a value between 1.3 and 1.5 in response to sharp deceleration of the vehicle, and a value between 1.0 and 1.2 in response to low deceleration of the vehicle.
In an advantageous further refinement of the present invention, the reference speed of the wheel is set equal to the speed of the wheel, when the speed of the wheel is greater than or essentially equal to the wheel reference speed obtained by interpolation.
In another advantageous refinement of the present invention, the speed of at least two vehicle wheels is ascertained, e.g. measured, and the reference speed of each side of the vehicle is ascertained, the reference speed of a wheel being determined as a function of the deceleration of the fastest wheel of the side.